Technical Field
The present invention relates to a Digital Rights Management (DRM) system used with the Digital Transmission Content Protection—Internet Protocol (DTCP-IP) standard to determine allowable copies of video to be made to client devices.
Related Art
Copy One Generation (COG) content now supports a counted copy use case, under the earlier-titled DTCP “plus” revision to DTCP-IP, now formally DTCP-IP 1.4.
In a typical counted copy control model with a maximum copy count, Max Count N, a Personal Video Recorder (PVR) is allowed to manage COG content copies as if it had a repository of N identical copies of the event. Each one would be marked on the PVR storage as copy no more (CNM) and could be transferred out under the DTCP Move transaction, and then deleted or disabled.
Any copy moved to another client device from the PVR would also be stored on that client device, and marked as CNM. As always, that copy could be further moved, but never copied. In this light, that copy can be moved back to the originating PVR, and again exist as a single copy on that drive along with the remaining copies.
DTCP copy management control allows a single one of N copies on the PVR to be stored, along with the parameter N, and a count, so long as the copy stored is exactly identical to the full N separate copies. This means a way to recognize when a copy is moved back is identical to the one already on the PVR is needed. This could be done by comparing the copy bit by bit to the one already present, and if identical, the moved back copy could be deleted and the existing copy count increased by one. This is what is called a “check in,” like a library loan. Note that a “Max Copy Count” of N means that the original copy on the PVR is one of the N copies. A count of the copies remaining to be issued would then also be maintained. Thus the original recording process means the PVR device has a Max Count=N, and a remaining copy count=N−1. When a copy is transferred to a first client mobile device, then the remaining copy count would be N−2.
Following this DTCP model exactly, any move back would take minutes, depending on the size of the asset and the Wi-Fi or other connectivity to the PVR from the client. This time delay is believed undesirable for many DTCP users. It is desirable to provide a DRM system to handle copy control using the DTCP standard that would allow a move back of a copy that would take a minimal amount of time.